The amount of waste water is rapidly increasing every year causing environmental pollution problems to become a major issue. Different kinds of efforts to effectively process waste water are ongoing.
As a representative example of such efforts, techniques used on a sludge dehydrating apparatus which removes water from sludge and makes sludge a cake of dehydrated sludge were proposed in Korean Patent Laid-open Publication No. 2002-0038426, No. 2002-0038427, No. 2003-0000984, No. 2003-0000985, etc.
FIG. 1 is a conceptual view of a conventional sludge dehydrating apparatus disclosed in the above-mentioned techniques. As shown in FIG. 1, in the conventional sludge dehydrating apparatus 100, fixed disks 110 and movable disks 120 are arranged in a row with gaps defined between the plates. A rotating rod 130 connects the movable disks 120 to each other. The movable disks 120 are rotated at the same time by the rotating rod 130 so that water is removed from sludge through the gaps. A screw 140 moves the sludge and compresses it, thus dehydrating the sludge. Here, the movable disks 120 use the power of a drive source 150 of the screw 140 to rotate.
However, in the conventional sludge dehydrating apparatus 100, the drive source 150 that drives the screw 140 is provided on only one side of the screw 140. In addition, the drive source 150 not only rotates the screw 140 but also rotates the movable disks 120 around the screw 140. Therefore, the torsion stress that is applied to a start point of the rotating rod 130 at which the power of the drive source 150 is applied to the rotating rod 130 differs from that applied to an end point of the rotating rod 130 which is the final recipient of the power.
If the sludge dehydrating apparatus 100 is small, in other words, is comparatively short, the possibility of the rotating rod 130 undergoing bending deflection is low. Thus, the movable disks 120 can be rotated at the same time without causing any problems so that the dehydrating operation can be carried out smoothly.
However, if the sludge dehydrating apparatus 100 is large and thus comparatively long, the rotating rod 130 may bend, thus making it difficult to smoothly dehydrate sludge. In detail, with the passage of time, the rotating rod 130 that was up to that point straight may bend at its portion that is far from the drive source 150. Hence, as distance from the drive source 150 increases, the efficiency of power transmission is reduced. As a result, the movable disks 120 that are positioned far from the drive source 150 cannot rotate normally resulting in the gaps possibly not being reliably defined between the plates, thus making the dehydration of sludge inefficient.
Furthermore, if the sludge dehydrating apparatus 100 is comparatively long and thus the screw 140 is also long, the drive shaft of the screw 140 may bend. Thereby, malfunction of the apparatus such as deformation of the fixed disks 110 and the movable disks 120 may result.
In the operation of the sludge dehydrating apparatus 100 which dehydrates sludge, if the screw 140 is rotated at low speed in order to enhance the efficiency of dehydration, a large load is applied not only to the screw 140 but also to the rotating rod 130, thus causing bending deflection of the rotating rod 130 that results in the above-stated problems.